1. Field of the Invention
This invention relates to a thermoplastic water-absorptive gel carrier for use as a carrier to which animal cells, plant cells, microorganisms and/o:- protozoans are fixed to obtain a bioreactor for substance production, harmful substance treatment, waste oil treatment, wastewater treatment, deodorization and the like.
2. Description of the Background Art
The carriers used in bioreactors are of two types: porous and gel (nonporous). Porous carriers include those made of polyurethane, cellulose, polypropylene, polyvinyl formal and ceramic.
The porosity of these carriers gives them a large surface area. They are frequently used with animal cells, plant cells, microorganisms and/or protozoans fixed to their porous surfaces.
Porous carriers have various disadvantages, however. Polyurethane and polypropylene porous bodies are hydrophobic and therefore have poor fluidity in water. In addition, they resist adherence of animal cells, plant cells, microorganisms and protozoans. Cellulose porous bodies are susceptible to erosion by such organisms and are therefore short in service life. Among other shortcomings, polyvinyl formal porous bodies have the drawback that no method has been established for their production on an industrial scale. Ceramic porous bodies are restricted in method of use since their high specific gravity prevents them from being fluidized in water.
Gel carriers include those made of polyacrylamide, polyethylene glycol, polyvinyl alcohol and alginic acid.
Although these gel carriers are generally used with animal cells, plant cells, microorganisms and/or protozoans fixed by envelopment within the gel, they can also be used with animal cells, plant cells, microorganisms and/or protozoans fixed to the gel surface.
Since these gel carriers contain water to a high degree, they exhibit high biocompatibility and offer a favorable habitat for animal cells, plant cells, microorganisms, and protozoans except for polyacrylamide gel carrier prepared from acrylamide, which is cytotoxic. On the other hand, most of these gel carries are inferior in physical strength owing their high water content. They are therefore highly likely to experience wear and breakage during use in the reactor.
Gel carriers reported to date, including those mentioned above, fall in the categories heat cured, low-temperature cured, ion-crosslinking cured and radiation cured organic polymer compounds.
Once these carriers have been formed into a specific shape, they cannot be remelted and changed into another shape. They are therefore usually cut to the desired size.
The process of cutting the water-impregnated and swollen gel into several millimeter sized cubes is very laborious. The production of conventional gel carriers has therefore been extremely troublesome and involved long production time and high cost. In addition, high volume production of the gels is difficult. These factors are believed to account for the failure of gel carriers to achieve wide utilization in bioreactors.
An object of the invention is to provide a bioreactor carrier made of thermoplastic water-absorptive gel which contains a high degree of water, has excellent physical strength, exhibits strong resistance to erosion by organisms, and can be readily produced industrially in high volume.